In screw centrifuges for the continuous separation of flowable substances of different kinds, one critical area is where the mixture inflow tube leads into the feed chamber, since portions of the mixture may flow back, because of turbulence or excessive throughput, into the cavity of a hollow shaft of a conveying screw and become deposited inside a cavity of the conveying screw. To remedy this problem, in known designs openings are provided in the wall of the hollow shaft of the conveying screw, through which openings these product deposits can escape into the region of the screw blade. However, product deposits may over time become baked into such cavity and in particular into dead spaces thereof, and thus produce an imbalance on the rotating conveyor screw.
Attempts have therefore been made to circumvent the problem of product deposits in the comparatively large cavity of the conveyor screw by mounting inside the hollow shaft a protective tube through which the mixture inflow tube leads to the feed chamber. The problem is only partially solved in this fashion, however, since the danger still exists that the comparatively narrow annular space between the protective tube and the mixture inflow tube may become clogged with back-flowing portions of the mixture.